1. Technical Field
The invention relates to a bank structure, a pattern forming method, a device, an electro-optical device, and an electronic apparatus.
2. Related Art
As a method of forming wiring composed of a predetermined pattern used for electronic circuits or integrated circuits, for example, photolithography is used widely. Photolithography requires large-scale apparatuses, such as a vacuum apparatus and an exposure apparatus. Also, there is a problem with the above apparatuses in that complicated steps are required in order to form wiring composed of a predetermined pattern, and the manufacturing cost is high because the use efficiency of a material for the wiring is merely about several percent and most of the material is consequently discarded.
To cope with this, a method of forming wiring composed of a predetermined pattern on a substrate using a droplet discharge method, i.e., a so-called ink jet method by which a liquid material is discharged in the shape of droplets from a liquid discharge head has been suggested (for example, refer to JP A-11-274671 and JP A-2000-216330). In this ink jet method, a liquid material for patterns (functional liquid) is directly disposed in patterns on a substrate, and thereafter heat treatment and laser irradiation are performed to form desired patterns. Accordingly, according to this method, since a photolithographic step becomes unnecessary and consequently a whole process can be simplified significantly and a raw material can be directly disposed in a pattern position, there is a merit that the amount used can also be reduced.
Meanwhile, in recent years, the densification of circuits which constitute a device has progressed, for example, the production of narrower and thinner wiring has been demanded. However, with the pattern forming method using the above-mentioned droplet discharge method, since a discharged droplet spreads on a substrate after it has landed on the substrate it is difficult to form a fine pattern stably. Particularly when a pattern is intended to be used as a conductive film, there is a possibility that a liquid pool (bubble) may be generated by the above-mentioned spreading of a droplet which causes defects, such as breaking of wires and short-circuiting. Thus, a technique using a bank structure provided with a wide wiring formation region and a fine wiring formation region formed to be connected to this wiring formation region has also been suggested (for example, refer to JP A-2005-12181). According to this technique, a functional liquid is discharged to the wide wiring formation region, and the functional liquid is allowed to flow into the fine wiring formation region by capillary action to form a fine wiring pattern.
Here, If the difference between the width of the fine wiring formation region and the width of a wiring formation region where a functional liquid is to be discharged becomes large, since the functional liquid generally flows along a bank which partitions off the wide wiring formation region, the amount of inflow of the functional liquid into the fine wiring formation region by capillary action will be insufficient. Then, there is a problem that the film thickness of a formed fine wiring pattern may become small compared with that of other wiring patterns. Thus, for example, a method in which a part of the wider wiring formation region is narrowed to increase the amount of inflow of the functional liquid from this wiring formation region to the fine wiring formation region to make the fine wiring pattern thick can be considered.
However, as described above, when the amount of the functional liquid which flows into a fine wiring formation region (first pattern formation region)is increased by narrowing a part of the wiring formation region (pattern formation region), it is difficult to appropriately regulate the amount of inflow of the functional liquid. For example, if an excessive amount of functional liquid flows into the wiring formation region, the film thickness of the fine wiring pattern will become thick compared with that of other wiring patterns. As a result, a difference will be caused in film thickness between the fine wiring portion and other wiring portions.
Then, for example, when this technique is intended to be applied to the formation of gate wiring and a gate electrode continuously connected thereto, the film thickness differs between the gate wiring and the gate electrode. As a result, stable transistor characteristics will be sufficiently acquired.